1. Field of the Invention
The invention relates to a drop weight for a tubular writing instrument, having a drop weight body and a cleaning wire fixed thereon, the drop weight body consisting of two parts. A lower part provides a front support surface for the support of the drop weight body in its frontal position inside the tubular writing instrument. The two parts are displaceable in relation to each other in the direction of the longitudinal extension of the cleaning wire, at least during a first operational state.
The invention further relates to a tubular writing instrument having a drop weight body located in an inner bore of a housing which is connected with a writing fluid supply chamber and which has in its front end a cleaning wire extending into the writing tube and having a drop weight retainer to limit the displacement of the drop weight body in the direction towards the writing fluid supply chamber.
2. Background of the Invention
In a known drop weight of this type (German Published Patent Application DE-OS 16 11 802), the part of the drop weight body having the front support surface is in the shape of a rod and has annular shoulders at both ends. The outer surface of the front shoulder constitutes a front support surface and the cleaning wire is fastened to this shoulder. An auxiliary weight is located on the rod-shaped section of the drop weight body and its length is less than the distance between the two shoulders on the main part of the drop weight body, so that the auxiliary weight part of the drop weight body is movable axially back and forth in relation to the main part. When a tubular writing instrument containing such a drop weight is shaken, impulses are created by the auxiliary weight part of the drop weight body, so as to improve the movability of the drop weight and more particularly to cause loosening of the cleaning wire, which perhaps might have become stuck in the writing tube because of dried writing fluid.
When manufacturing tubular writing instruments having a cleaning wire extending inside the writing tube, it is necessary to set the length of the cleaning wire so that an exactly defined projection of the front end of the cleaning wire beyond the front end of the writing tube results when the drop weight is supported by its front support surface inside the tubular writing instrument. Because the front end of the cleaning wire must also be rounded to prevent scratching of the writing or drawing surface, setting of the desired distance is difficult. It is not possible to manufacture the cleaning wire first with a considerably increased projection and then simply cut the wire to the desired length, after insertion into the tubular writing instrument.
For setting the desired projection of the cleaning wire beyond the front end of the writing tube it is also already known (German Published Patent Application DE-OS 34 34 188) to use an external screw thread, ending at a rear stop. The rear stop supports a drop weight body as a drop weight restraint inside a tubular writing instrument to limit the axial back and forth movement, and to fix the position of the drop weight restraint in a manner resulting in a desired extended length of the cleaning wire. However, to do this a special support for the drop weight body is required on the one hand and, on the other, a specially shaped drop weight restraint must be fixed inside the tubular writing instrument in a particular manner.
In that known tubular writing instrument (German Patent Published Application DE-OS 34 34 188), the drop weight restraint is fixed, by means of a threaded bush, into the housing in such a way that the exact desired projection of the cleaning wire beyond the front end of the writing tube is attained, after which the threaded bush is permanently fixed in the housing.
In such a writing tube it is therefore possible to set the correct projection of the cleaning wire beyond the front end of the writing tube exactly, without the requirement of treating the front end of the cleaning wire. After assembly, the drop weight body, together with the drop weight restraint, can be screwed out of the housing and can also be re-inserted into the housing. When re-inserted, the exact and correct projection of the cleaning wire beyond the front end of the writing tube is again attained.